Abstract: Apparatus and method for monitoring the sensory system of a patient to enable determination of the level and depth of spinal and epidural nerve blocks, including those induced by anesthetics administered to a patient, which blocks affect the sympathetic and motor nervous systems. The anesthesia level is sequentially and repeatedly scanned at a plurality of spaced points to provide a continuous determination of the extent and depth of superficial and deep sensation and sympathetic and motor integrity. The electronic apparatus includes a stimulator that provides selective stimulation to each element of a multiple element transmitting unit the elements of which are non-invasively positioned contiguous to the skin of a patient, and a physiological response detector to detect patent responses to stimulation sensed by the elements of a multiple element sensing unit the elements of which are also non-invasively positioned contiguous to the skin of the patient.